Since the introduction of packet data services in 3GPP (e.g., GSM and WCDMA), mobile users are virtually always connected and reachable via their mobile devices, which are referred to generally as user equipment (UE). That is, it is becoming more and more common for UEs to be able to receive content at any time. A growing number of content distribution services offered by mobile networks involves group of users interested in receiving similar content (e.g., sports events, news). As long as the group sizes are small and the densities are low, unicast channels can be used to distribute the content. However, the sizes of such groups are generally increasing, making the use of unicast channels problematic. In addition, the content that is distributed is generally requiring increasing amounts of bandwidth as the content shifts from text to multimedia, further exacerbating the problems associated with the use of unicast channels. Thus, instead of using unicast channels to distribute content to groups of mobile users, it is becoming increasingly desirable to distribute content only once to all users simultaneously using broadcasting and multicasting techniques. Multicasting directs content to plural specific subscribers. In contrast, broadcasting provides content that can be accessed by anyone with suitable equipment.
A new service, called multimedia broadcast multicast service (MBMS), is being developed for both broadcasting and multicasting content to mobile users. MBMS introduces support for IP multicast services into the GSM and WCDMA architecture and standardizes the necessary adaptations to cope with the particularities of mobile systems. MBMS is described, e.g., in 3GPP TS 25.246 v6.3.0 (2004-06), 3rd Generation Partnership Project Technical Specification Group Services and Systems Aspects; Multimedia Broadcast/Multicast Service (MBMS); Architecture and functional description (Release 6).
As shown in FIG. 1, the MBMS system can be divided into three functional layers: a bearer service 100, a delivery method 110, and user services 120. The MBMS bearer service 100 provides the mechanisms to transport multicast and broadcast IP data to User Equipments (UE) efficiently. The delivery method 110 can either comprise a download delivery method 112 or a streaming delivery method 114. Delivery methods may use one or many MBMS bearer services, as well as point-to-point bearers, to deliver data. User services 120 enable applications on top of MBMS and may use one to many delivery methods to deliver the application data. MBMS employs two new contexts: a MBMS Bearer context and a MBMS UE context. The latter is kept together with the mobility management contexts in the serving nodes. One MBMS UE context exists for each MBMS group that each terminal has subscribed to. It contains the IP multicast address and Access Point Name (APN) identifying the MBMS bearer that is used. The bearer context also contains a Temporary Mobile Group Identity (TMGI), which is assigned to all the UEs in the same MBMS group, the state of the bearer, QoS attributes, the list of downstream nodes and the UEs hosted by this particular node.
MBMS sessions are set up between a broadcast-multicast service center (BM-SC), a gateway General Packet Radio Service (GPRS) support node (GGSN), and the UE. The MBMS delivery method is triggered by the MBMS user service provider. An MBMS session can comprise multicast or broadcast sessions. In the broadcast mode, the UE performs a local activation of the service independently of the session start at the BM-SC. In the multicast mode, the UE has to first subscribe to the service in order to join a multicast group. Group membership information is maintained in each intermediate node on the transmission path. The information is stored in MBMS specific contexts, which are located in the BM-SC, the GGSN, SGSN and the RNC.
Currently, there is no provision to allow UEs to define a multicast group and transmit content to that group without going through the BM-SC, which can be a relatively difficult and cumbersome process for the average user. UEs, however are increasingly capable of storing and disseminating large quantities of content and users of such devices increasingly desire to share such content with other mobile users.
Accordingly, it would be desirable to provide a method and apparatus that allows a UE to serve as a source of multicast/broadcast content in a MBMS system in a relatively simple and convenient manner.